Measurement methods of the stresses exerted on rails by the vehicles that travel on them exist and, therefore, they form part of the state of the art. Said methods show the placement of multiple extensometric sensors (strain gauges) in certain configurations to be able to obtain track compression values, and the bending moment.
The use of extensometric sensors allows measuring the elongation of the sensor which, as they are fixed to the rail in a specific position, measure the elongation of said rail. The combinations used in the known methods are performed by combining pairs of extensometric sensors placed on both sides of the track and connected together forming a Wheatstone bridge, or half Wheatstone bridge, to directly measure the forces exerted on the rail.
As indicated, in the known methods various pairs of said strain gauges must be placed connected together to be able to directly obtain the values of the measurements sought in said known configuration, such as, for example, pairs of parallel strain gauges, connected to pairs of strain gauges parallel to the other side of the rail, and pairs of perpendicular strain gauges connected to pairs of strain gauges perpendicular to the other side of the rail.
Said configuration involves the need to use a greater number of extensometric sensors, one or more pairs of strain gauges to have a measurement channel, and the need to join said strain gauges on both sides of the rail having, in most cases, to drill the rail, so that said methods are a considerable cost in devices and a cost in installation time, being multiplied when performing this measurement simultaneously at various points of rail stretches.
The use of Wheatstone bridges to measure lateral forces directly is also known but makes necessary the placement of various pairs of strain gauges connected together, which in said methods are placed on the rail runners feet, something which does not allow taking measurements with sufficient accuracy since the runner foot is much more rigid, with respect to the track web and the electrical signal obtained is foreseeably of worse calibration quality. There is the possibility of indirectly obtaining, via calculation of a finite element method, an approximation of the lateral force, based on known methods that measure bending and compression moments, but as indicated they are indirect approximate methods.